The antagonistic relationship on cytolysis of bacterial protoplast and rabbit red blood cells between serum calcium-decreasing active lipoprotein α-I, which was obtained from culture filtrate of Bacillus subtilis K., and surfactin was investigated. a-I showed an inhibitory effect against the lytic activity of surfactin. Even if α-I and rabbit red blood cells were preincubated, α-I did not bind with red blood cells and remained in the supernatant. Consequently, the mechanism of antagonism between α-I and surfactin was found to be the association of α-I with Surfactin. This was also ascertained by gel filtration. On the other hand, α-I and Surfactin had no antimicrobial activity against Bacillus subtilis. Examination of the production patterns of these substances showed, that the surface activity increased rapidly in the culture medium during the logarithmic growth phase, and the antagonist α-I Was released during the stationary phase and the autolysis period, accompanied with spore formation. These results suggest that α-I and Surfactin were required as regulating factors on the growth and autolysis of Bacillus subtilis.
